Glass composition



United States Patent 2,912,339 GLASS COMPOSITION E. Duncan, Plate Glass No Drawing. Application January 13, 1954 Serial No. 403,908

12 Claims. (Cl. 106-53) The present invention relates to a family of glass compositions suitable to provide a series of opaque glasses having a steel gray color. Glasses of this type are manufactured by either the pot casting method or in continuous furnaces and are sold under the tradename of Gun Metal Carrara. They are used for interior decorative purposes, such as bathroom and kitchen walls, and for exterior walls, such as store and service station fronts.

We have found previously that a pleasing opaque grayish color can be imparted to glasses used for structural decorative purposes by adding fluorides to opacify the glass and a mixture of minor proportions of nickel,

chromium and cobalt oxides to provide the desired color.

However, the presence of chromium in the glass batch is looked upon with disfavor by glass fabricating personnel, because chromic oxide has a high melting point and is not very soluble in molten glass and also because the chromium varies in color between a yellowish-green and a bluish-green depending upon the oxidizing conditions present. j v

An object of the present invention is to provide opaque glasses substantially free of chromium, having a permanent, uniform gray color, good mechanical strength, resistance to weathering and staining, freedom from bubbles and other imperfections, and fabricable in relatively large quantities by such processes as are used tomanufacture plate glass.

The basic glasses included in the present invention contain SiO from about 55 to about 75% by weight; Na;,0 to 15%; K 0 0 to 0 to 10%; PhD 0 to 5%; and Sb O or As O or combinations thereof 0 to 2%; F 0.5 to 5% and C00 0 to 0.05% by weight.

Silica is the principal glass former. of SiO of between 55 and 75 composition. The durability of glass containing less than 55% SiO is poor and such glass is likely to stain when exposed to weather. Furthermore, it is diflicult to melt a glass composition including over 75 SiO There is also a tendency for glass containing more than the desired maximum of SiO to devitrify.

The alkali metal oxides, Na O and K 0 are the principal fluxes. Li O may also be used to replace part or all of the N a o and K 0. However, the use of this material increases the cost of the batch and therefore we prefer to have between 11 and 21% by weight of a combination of Na O and K 0. Glass having less than 11% of Na O and K 0 is difficult to melt. Glass has poor durability when the total alkali metal oxide content exceeds 21% 1 to 6%; M0 0.2 to 1%; CuO' such crystals and is by weight. Further, an excessive amount of alkali metal oxide may adversely affect opacification of the glass.

The A1 0 is desired to increase the length of the working range of the glass. If more than 12% A1 0 is included in the glass, an excessive amount of alkali and fluorine is required to compensate for the excess stiffness imparted to the glass by the alumina. Glasses having less than 2% A1 0 by weight are characterized by an undesirable working range.

In our glasses, fluorine serves both as an opacifying agent and as a flux. As an opacifying agent, it produces fluoride crystals which form in the glassy matrix. The

opacity of the glass depends on the size and number of also a function of annealing. The careful control of opacification thus is mostimportant to our glasses since it actually aflects the structure of the material. It is apparent that the use of too much fluorine in these glasses will cause the formation of a glass unfavorably rich in fluoride crystals. This condition introduces whiteness sufficient to alter the color of the glass from the desirable uniform blue gray. Also, excessive opacity can alter the color of the glass by causing it to I absorb minute quantities of polishing agents during surfacing operations.

By contrast, when our glasses are deficient in fluorine, the color is less uniform and has too much depth while the glass reflects too little of the incident light, and may even transmit some light. In its role as a flux, fluorine helps greatly to melt and homogenize the'various batch materials since it not only decreases the viscosity of the glass at high temperatures, but also assists in freeing the molten batch of bubbles because a certain amount of thefluorine is evolved as a gas. Obviously, the use of i at least 1% by weight of fluorine is a requisite to the wherein the total alkali is-not less than 11% nor more than'21%; A1 0 2 to 12%; CaOf I crystals than We prefer a range V 7 Up to 10% 45 making of our glasses. Likewise, for the reasons set forth above, not more than 6% by weight of fluorine should be employed In actual practice, we prefer to have between 2.0% and 3.0% by weight-of fluorine in our glasses, although as stated, up to 6% by weight or as low as 1% by weight may be used depending on the percentages of the other constituents, the manner the glass is cooled during annealing and the intensity of the color required.

by weight of CaO may be employed. CaO tends to produce a more uniform opacity in the glass because it promotes the formation of smaller fluoride are produced in CaO-free glass. However, CaO -containing glasses require more fluorine than Ca0- free glasses, if a given level of opacity is to be maintained. Glass having above 10% C210 cannot be made of satisfactory opacity unless an extremely high percentage of fluorine is used and this results in a glass of poor durability. We prefer a glass which contains approximately 4 to 6% by weight of CaO in order to maintain a proper balance between the alkali and the fluorine content for optimum glass durability and in order to provide a means of regulating the opacity of the glass. Other bivalent metal oxides such as PbO, MgO, ZnO and BaO may also be substituted for part or all of the CaO and when such substitutions are made, the maximum total weight of the bivalent metal oxides may be increased to about 12% by Weight. In general, we have found that the increased cost of these other materials does not justify their use.

The use of lead oxide is an exception, because the presence of PbO in the glass composition enhances the uniformity of distribution of the colorants throughout the volume of the glass being formed. Failure to include melting method. The temperature of annealing is set forth in detail on page 12, Section Bl, of the Glass Manual and page 30, Section B1 gives the speeds through the lehr. The glass is at a temperature of about 1500 F.

lead oxide may result in a variation in color in the finished 5 entering the lehr and cools rapidly to about 1150" F, glass product and, specifically, may cause the formation then very slowly to 950 F. and then rapidly again to of a transparent layer adjacent to the surfaces of the glass room temperature. The temperature range from 1l50 when it is formed as a sheet. Hence, the use of lead F. to 950 F. is known as the annealing range. It is duroxide is justifled despite its relative high cost compared ing this conventional annealing that the glass opacifies to lime. and receives its final color. The glass proceeds through Arsenic and antimony are used as refining agents to the lehr at a rate of about 108 inches per minute during aid in removing undissolved gases from the molten glass. the annealing. More than 2% of either refining agent does not appear The desired steel gray color which is produced, results to be beneficial to the finished glass composition, but we from the mixture of the colors imparted to the glass by prefer not to exclude them entirely from the glass because the nickel, copper, and cobalt colorants utilized and the Streaky, non-uniformly colored glass is the result of such white color produced upon crystallization of the fluorineexclusion. containing compounds. Therefore, it is necessary to The amount of fluorine present in the glass composition have suificient colorants to provide a uniform coloring must be delicately balanced with the amount of nickel, and sufiicient fluorine to provide uniform opalescence, copper and cobalt present. The balance between the throughout the volume of the composition. fluorine and the coloring agents is necessitated by the The desired neutral or steel gray color is imparted to manner in which the glass is made. Raw batch materials the glass by a combination of NiO and CuO, to which are thoroughly mixed before being fused together to form small quantities of 000 may be added. The relative molten glass. After melting, the glass is refined to remove proportion by weight of the copper oxide and nickel oxide occluded gases. The refined glass is withdrawn from the preferably ranges between about 1:1 and 10:1 in order furnace, formed into a sheet, and introduced into an anto provide the desired coloring to the glass composition. nealing lehr where it is cooled. During this cooling In any event, the total amount of nickel plus copper comoperation, the glass is annealed, the fluoride crystals are puted as the respective oxides is preferred to be between formed, and the color develops as a result of using a comabout 1% and 6% by weight of the glass composition. bination of the proper proportions of fluorine and the Some C00, not exceeding .05% by weight of the comother colorants. position, may be included in order to impart a slightly A description of the method of making a Carrara glass stronger bluish tint to the blue-gray color produced by such as the glass of the present invention is given in US. the colorants. The total percentage of nickel computed Patent No. 2,776,900 granted to James E. Duncan and as NiO, copper as G10, and cobalt as C00 is required to Samuel L. Seymour and assigned to Pittsburgh Plate be of the same order of magnitude as the percentage of Glass Company. A more detailed description of the fluorine contained in the opacified gray glass produced. commercial method of making Carrara glass as employed The total weight percentage of the coloring ingredients by the Pittsburgh Plate Glass Company is set forth in the h uld not be more than about 50% by weight above or Glass Manual published by Pittsburgh Plate Glass Combelow the weight percentage of fluorine in order to insure pany and copyrighted in 1946. The base composition of that the proper degree of uniformity of color is obtained Carrara glasses, together with numerous colorants which and the color has the requisite opacity. may be added thereto, is set forth on page 5, Section The following batch compositions listed in TableIwere 13-2 of the Glass Manual, and on page 4 of Section B-Z. used in the preparation of suitable decorative opaque The method of making Carrara glass is referred to as the glasses having a homogeneous gray color, the calculated pot melting process which is employed for making plate compositions of which are listed in Table II.

Table 1 Parts by weight Ingredient Batch Batch Batch Batch Batch Batch Batch #1 #2 #3 #4 #5 #6 #7 Sand 958 95s 95s 958 958 95s 95s Soda Ash 336 326 326 326 336 340 33s Feldspar 900 900 900 900 900 900 900 Fluorspar (OaFr)- 155 165 165 165 155 151 155 Sodium Nitrate..- 50 50 50 50 50 50 Litharge (PbO) 60 so 60 60 66 66 Antimony Oxide (SbzO 10 15 15 15 15 15 15 Nickel Oxide (green). 11.5 9.6 18 14.4 9.6 9.6 9.6 Copper oxide 46 67. 6 24 38. 4 57. 6 57. 6 57. 6 Cobalt oxide 0.06 O 0 0 0 ,19

glass. Manufacture begins with preparation and melting of the batch followed by the casting of the molten glass, annealing and the final step of grinding and polishing the rough product as it comes from the annealing lehr. The pot melting process is described in detail on pages 24 to 30, Section B-l, of the Glass Manual.

A Carrara glass becomes milky while it is being annealed due to the action of fluorine which has an opalizing, opacifying effect according to column 1, page 5, Section 13-2 of the Glass Manual. This annealing is the same as is employed in the commercial manufacture of plate glass, whether made by the pot melting or tank ingredients.)

Table II Parts by Weight Ingredient O O G C omp. omp. omp. omp. Comp. Comp. Comp. #1 #2 #3 #4 #5 #6 #7 .34 65. 76 66. 47 66. 16 65. 90 65. 96 65. 89 27 9. 92 10. 03 9. 98 10. 18 10. 29 10. 18 .16 4.12 4.16 4.16 4.13 4. 13 4.13 .79 6. 73 6.80 6. 77 6. 74 6. 75 6. 74 58. 4. 90 4. 95 4. 93 4. 62 4. 50 4. 62 48 2. 62 2. 65 2. 64 2. 47 2. 41 2. 47 54 2. 52 2. 55 2. 63 2. 53 2. 53 2. 53 .42 .63 .64 .63 .63 .63 .63 1 47 39 74 59 39 39 39 1.94 2. 41 1. 01 1. 61 2. 41 2. 41 2. 41 C d0 003 008 Luminous reflectance based on illuminant O 1. 4 2. 3 1. 2 l. 7 1. 8 1. 8 Trlchromatic coefi'icients.

. 2618 273 273 258 253 2893 281 285 274 276 z .4489 .446 .442 .468 .471 Excitation purity 26. 8 19. 17. 5 17. 0 23. 5 25. 0 Dominant Wavelength, mm. 280 484 478 480 480. 5 482 The following table of reflectance characteristics of composition number 2 relative to MgO at various wavelengths within the visible spectrum is included for additional information concerning the optical characteristics obtained in a particular glass. It is desired that the percent reflectance be kept under throughout the visible spectrum for any glass produced according to our invention. f

Wavelength (millimicrons): Percent Reflectance 400 8.9 420 4.6 440 3.0 460 2.6 480 2.7 500 2.7 520 2.7 540 2.6 560 2.3 580 2.1 600 1.8 620 1.4 640 1.2 660 1.2 680 1.2 700 1.1 720 1.1 740 1.0 750 1.0

It is understood that various modifications of ingredients Within the ranges may be made without departing from the spirit of the present invention. It is understood that slight modifications in the amounts of various batch ingredients are required to form glass compositions within the desired range, depending upon the exact shade of gray and other characteristics desired. It is also understood that susbtitutions may be made in the various materials recited for the batch to provide the desired ingredients, but that the batch materials listed are the least expensive sources of these ingredients.

What is claimed is:

1. A glass having a calculated composition consisting essentially of SiO;; 66.34% by weight, Na O 10.27% by weight, K 0 4.16% by Weight, A1 0 6.79% by weight, CaO 4.58% by weight, F 2.48% by weight, PbO 2.54% by weight, Sb O .42% by weight, NiO .47% by weight, CuO 1.94% by weight and C00 003% by Weight.

2. A glass having a calculated composition consisting essentially of SiO 65.76% by weight, Na O 9.92% by weight, K 0 4.12% by weight, A1 0 6.73% by weight, CaO 4.90% by weight, F 2.62% by weight, PbO 2.52% by weight, 815 0 63% by weight, NiO 39% by weight, and CuO 2.41% by weight.

3. A glass consisting essentially of 55 to 75% by weight SiO 11 to 21% by weight of alkali metal oxides selected from the group consisting of 5 to 15% by Weight Na O, 0 to 10% by weight K 0 and 0 to 15% by weight L120, 0 to 12% by weight of bivalent metal oxides selected from the group consisting of 0 to 10% by weight CaO, 0 to 5% by weight PbO, 0 to 12% by Weight ZnO, 0 to 12% by Weight BaO, and 0 to 12% by weight MgO, 2 to 12% by Weight A1 0 1 to 6% by Weight F 0.2 to 1.0% by weight NiO, 0.5 to 5.0% by weight CuO and 0 to 0.05% by Weight CoO, the total combined weight of NiO, CuO and C00 being not more than 50% by weight above or below the weight percentage of fluorine.

4. A glass such as recited in claim 3 wherein the CaO content is between 4% and 6% by weight, the PhD is between 2% and 3% by weight and F is between 2% and 3% by weight.

5. A glass such as recited in claim 3 wherein the total combined weight of CuO, NiO and C00 ranges from about 1 to 6% by weight.

6. A glass such as recited in claim 3 wherein the trichromatic reflectance coefiicients are within the following limits:

xbetween 0.25 and 0.28 ybetween 0.26 and 0.29

7. A glass such as recited in claim 3 wherein the amount of CuO is between about 1 and 10 times the amount of M0 by weight.

8. A glass consisting essentially of 55 to 75% by weight SiO 11 to 21% by weight of alkali metal oxides selected from the group consisting of 5 to 15% by weight Na 0, 0 to 10% by weight K 0 and 0 to 15% by weight Li O, 0 to 12% by weight of bivalent metal oxides selected from the group consisting of 0 to 10% by weight CaO, 0 to 5% by weight PbO, 0 to 12% by Weight ZnO, 0 to 12% by weight BaO, and 0 to 12% by weight Mg(), 2 to 12% by weight A1 0 0 to 2% by weight of refining agents, 1 to 6% by weight F 0.2 to 1.0% by weight NiO, 0.5 to 5.0% by weight CuO and 0 to 0.05% by weight C00, the total combined weight of NiO, Cut) and C00 being not more than 50% by weight above or below the weight percentage of fluorine.

9. A glass consisting essentially of 55 to 75% by weight SiO 11 to 21% by weight of alkali metal oxides selected from the group consisting of 5 to 15% by weight Na O, 0 to 10% by weight K 0 and O to 15 by weight Li O, up to 12% by weight of bivalent metal oxides selected from the group consisting of 0 to 10% by weight CaO, 0 to 5% by weight PbO, 0 to 12% by weight ZnO, 0 to 12% by weight BaO, and 0 to 12% by weight MgO, 2 to 12% by weight Al O 1 to 6% by Weight F 0.2 to 1.0% by weight NiO, 0.5 to 5.0% by weight CuO and to 0.05 by weight C00, the total combined weight of NiO, CuO and C00 being not more than 50% by weight above or below the weight percentage of fluorine.

10. A glass consisting essentially of 55 to 75% by weight SiO 11 to 21% by weight of alkali metal oxides selected from the group consisting of to 15% by weight Na O, 0 to by weight K 0 and 0 to by weight Li O, up to 12% by weight of bivalent metal oxides selected from the group consisting of 0 to 10% by weight CaO, 0 to 5% by weight PhD, 0 to 12% by weight ZnO, 0 to 12% by weight BaO, and 0 to 12% by weight MgO, 2 to 12% by weight A1 0 0 to 2% by weight of refining agents, 1 to 6% by weight P 0.2 to 1.0% by weight NiO, 0.5 to 5.0% by weight CuO and 0 to 0.05% by weight C00, the total combined weight of NiO, G10 and 000 being not more than 50% by weight above or below the weight percentage of fluorine.

11. A glass consisting essentially of the following ingredients in percent by weight: 55 to 75% SiO 5 to 15% Na O, 0 to 10% K 0, the sum total of alkali metal oxides being 11 to 21%, 2 to 12% A1 0 0 to 10% CaO, 0 to 5% PhD, 1 to 6% P 0.2 to 1.0% NiO, 0.5 to 5.0% CuO, and O to 0.05% CoO, the total combined weight of NiO, CuO and C00 being not more than by weight above or below the weight percentage of fluorine.

12. A glass consisting essentially of the following in-v gredients in percent by weight: to SiO 5 to 15% Na O, 0 to 10% K 0, the sum total of alkali metal oxides being 11 to 21%, 2 to 12% A1 0 0 to 10% CaO, e m 5% PbO, 0 to 2% 513 0 1 to 6% F 0.2 to 1.0% NiO, 0.5 to 5.0% CuO, and 0 to 0.05% C00, the total combined weight of NiO, C and C00 being not more than 50% by weight above or below the weight percentage of fluorine.

References Cited in the file of this patent FOREIGN PATENTS 430,387 Great Britain 1935 

1.
 3. GLASS CONSISTING ESSENTIALLY OF 55 TO 75% BY WEIGHT SIO2 11 TO 21% BY WEIGHT OF ALKALI METAL OXIDES SELECTED FROM THE GROUP CONSISTING OF 5 TO 15% BY WEIGHT NA2O, O TO 10% BY WEIGHT K2O AND O TO 15% BY WEIGHT LI2O, O TO 12% BY WEIGHT OF BIVALENT METAL OXIDES SELECTED FROM THE GROUP CONSISTING OF 0 TO 10% BY WEIGHT CAO1 O TO 5% BY WEIGHT PBO, O TO 12% BY WEIGHT ZNO, O TO 12% BY WEIGHT BAO, AND O TO 12% BY WEIGHT MGO, 2 TO 12% BY WEIGHT AL2O3, 1 TO 6% BY WEIGHT F2, 0.2 TO 1.0% BY WEIGHT NIO, 0.5 TO 5.0% BY WEIGHT CUO AND 0 TO 0.05% BY WEIGHT COO, THE TOTAL COMBINED WEIGHT OF NIO, CUO AND COO BEING NOT MORE THAN 50% BY WEIGHT ABOVE OR BELOW THE WEIGHT PERCENTAGE OF FLUORINE. 